This invention relates to an apparatus for adjusting the cant of the axis of rotation of an annular article with respect to a fixed axis, such as the axis of a vehicle axle or a test machine axle. More particularly, this invention relates to an apparatus for adjusting the camber and/or the slip angle of a mounted pneumatic tire.
In many applications there is a need to adjust the cant of the axis of rotation of an annular article with respect to a fixed axis. One such application is the need to adjust the camber and/or the slip angles of a mounted pneumatic tire for testing. By varying the camber and the slip angles of the tire, tire designers can determine how the particular tire reacts under given conditions. The data obtained from these tests is helpful in designing tires with an improved working footprint. To aid tire designers in quantifying the test data, SAE J670e Vehicle Dynamics Terminology is used as a standard coordinate system. Another application where there is a need to adjust the camber and/or the slip angle of a mounted pneumatic tire is on a vehicle. In racing vehicles, the camber and the slip of each tire may be individually adjusted for specific track conditions. On a passenger vehicle, the camber and ship may be similarly optimized.
A spindle is a mechanism used to hold a wheel to a vehicle or a tire testing machine. The center axis of the spindle is normally the axis of rotation for the wheel, and thus for the tire. The angle of rotation of the wheel can be adjusted with respect to a fixed axis, such as the axis of a vehicle axle or a test machine axle. The ease of adjusting the cant of the wheel with respect to the fixed axis is important. On vehicles, the cant of the wheels may be adjusted by adjusting the tie rods. However, adjusting a tie rod adjusts the cant of both wheels that correspond to that tie rod, an act that, at times, may be undesirable. On tire testing machines, many spindle assemblies must be dismantled and reassembled at the new desired cant because of their inability to be adjusted.
U.S. Pat. No. 3,999,429 entitled xe2x80x9cTIRE TESTING APPARATUSxe2x80x9d shows a spindle apparatus having a bearing that allows the camber and the slip angle of the tire to be varied. The adjustment of each angle is made by means of two screw-threaded members. Although the patent mentions the spindle as being adjustable, no details are given explaining how the adjusting mechanism works or is controlled. Additionally, the patent gives no information concerning how the given angles are locked into place or how the spindle supports the forces applied by the test vehicle or the tire test machine.
U.S. Pat. No. 5,481,907 entitled xe2x80x9cTIRE TESTING SYSTEM HAVING FOCUSED LINKS REDUCING COSINE ERRORSxe2x80x9d, provides for a tire testing system where both the camber and slip angles are adjustable. The camber and the slip angles are adjusted by the operation of actuators. The patent does not disclose a means of determining the angle of camber and/or slip applied or a means locking a specified camber or slip angle in place. Additionally, since the system is constructed of a number of links, cosine errors, even though reduced in this invention, still occur.
The apparatus of the invention allows the cant of the axis of rotation of an annular article to be adjusted with respect to a fixed axis. The apparatus has at least one set of wedge rings that are disposed between a back plate and a spindle plate. The back plate, furthest from the annular article, is fixed with respect to the fixed axis and the spindle plate is fixed with respect to the axis of rotation of the annular article. Each wedge ring has a wider portion and a narrower portion.
In the preferred embodiment, the back plate that is fixed with respect to the fixed axis is a second back plate. The spindle plate that is fixed with respect to the axis of rotation of the annular article is a first spindle plate. The apparatus also has a first back plate and a second spindle plate. The first spindle plate is connected to the first back plate. A first set of wedge rings is disposed between the first spindle plate and the first back plate. The second spindle plate is attached to the first back plate. The second spindle plate also is connected to a second back plate, which is located on a side of the second spindle plate opposite the first back plate. A second set of wedge rings is disposed between the second spindle plate and the second back plate.
For ease of understanding this disclosure, the following terms are defined.
xe2x80x9cCamberxe2x80x9d or xe2x80x9ccamber anglexe2x80x9d means the inclination or tilt of a tire with respect to a plane perpendicular to the ground at a particular point in time when the tire is in motion. It is considered positive when the wheel leans outward at the top and negative when it leans inward. The camber angle is sometimes referred to as the xe2x80x9cinclination angle.xe2x80x9d
xe2x80x9cCantxe2x80x9d means an inclination from a given line or a fixed axis. When used as a verb, cant means to set at an angle.
xe2x80x9cEquatorial plane (EP)xe2x80x9d means the plane perpendicular to the tire""s axis of rotation and passing through the center of its tread.
xe2x80x9cFootprintxe2x80x9d means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under normal load and pressure or under specified load, pressure and speed conditions.
xe2x80x9cLateralxe2x80x9d means an axial direction.
xe2x80x9cPneumatic tirexe2x80x9d means a laminated mechanical device of generally toroidal shape, usually an open-torus, having beads and a tread and made of rubber, chemicals, fabric and steel or other materials. When mounted on a wheel of a motor vehicle, the tire through its tread provides traction and contains the fluid that sustains the vehicle load.
xe2x80x9cSlipxe2x80x9d or xe2x80x9cslip anglexe2x80x9d means the angle between the direction of wheel heading, the X-axis and the direction of wheel travel. The direction of wheel heading is generally in the plane formed by the equatorial plane of the tire.